Fishing by hook of predatory fresh water and sea fish is from an economic standpoint the most profitable and from a sports standpoint, the most attractive. Predatory fish belong to a range of largest and strongest fish for which special equipment is required, in order to attract fish of prey and to hold them on a hook till drawing them out of the water. Predatory fish have in their jaws bone growths in the form of teeth for cutting and tearing their catch. Therefore these lower parts of line resp. casts, represent one of the most loaded part of fishing equipment for fishing predatory fish, because they are subjected to large tensile and gliding strains. Lines in general should be made of transparent materials, invisible in water, so that bait on lines would leave as natural an impression as possible. As there are not available materials for line with high tensile and gliding strength invisible in water, the lower, most strained parts of line are made of nontransparent, metal materials. Visible casts made of metal protruding from artificial or natural bait, decrease the attractiveness of the bait and thus the entire fishing event as an economic or sport activity. Therefore it is a technical problem of a device of manufacture that the lower reinforced nontransparent metal part of the line, be made invisible in a stage of attracting fish and effective and resistant to tensile and gliding strains in stages of swallowing, pulling off and dragging the bait.